1. Field of the Invention
The present invention is in the field of polymer interlayers and multiple layer glass panels comprising polymer interlayers, and, more specifically, the present invention is in the field of polymer interlayers comprising multiple thermoplastic layers
2. Description of Related Art
Poly(vinyl butyral) (PVB) is commonly used in the manufacture of polymer layers that can be used as interlayers in light-transmitting laminates such as safety glass or polymeric laminates. Safety glass often refers to a transparent laminate comprising a poly(vinyl butyral) layer disposed between two layers of glass. Safety glass often is used to provide a transparent barrier in architectural and automotive openings. Its main function is to absorb energy, such as that caused by a blow from an object, without allowing penetration through the opening or the dispersion of shards of glass, thus minimizing damage or injury to the objects or persons within an enclosed area. Safety glass also can be used to provide other beneficial effects, such as to attenuate acoustic noise, reduce UV and/or IR light transmission, and/or enhance the appearance and aesthetic appeal of window openings.
Safety glass is particularly desirable in architectural glazing applications that are intended for use in areas prone to hurricane activity. During hurricanes, wind-borne debris will be present. To protect a building during hurricane from being damaged, windows and doors, typically the weakest link in a building's envelope, must be safeguarded from penetration by wind-borne debris, and they must also remain in the place through the remainder of the storm. Therefore, an interlayer that can safeguard a window against significant impacts and remain in the opening during cyclical wind loading even if the glass is cracked is particularly desirable.
Attempts to create such an interlayer for hurricane protection have usually involved balancing the benefit to high impact resistance obtained from using a relatively softer and lower glass adhesion polymeric interlayer with the benefit of high cyclical wind loading resistance after glass cracking which is obtained from using a stiffer and high glass adhesion polymeric interlayer.
If an interlayer is too soft or adhesion to glass is too low, then the interlayer will not have the strength to resist high wind loading after an impact. On the other hand, if the interlayer is too stiff and adhesion to glass is too high, then the interlayer will not have a high level of impact resistance—i.e., the interlayer will have low penetration resistance.
Therefore, further improved interlayer compositions are needed to provide multiple layer safety glass that has high impact resistance and high cyclical wind-loading resistance for, among other things, hurricane protection.